The present invention relates to an improved method and apparatus for pre-impregnating glass or synthetic fibers with a curable, non-aqueous chemical treatment, and more particularly, to such a method which may be performed in-line with the glass forming process.
Glass fibers are commonly manufactured by supplying molten glass to a bushing, drawing glass fibers from the bushing, and applying an aqueous size to the fibers with an applicator roll. The fibers are then packaged and dried for further processing.
In order to fabricate composite parts, the fibers are often further chemically treated in an off-line process with a curable resin. The resins may be thermosetting or thermoplastic and may be either aqueous based or totally organic. For example, continuous glass fibers may be treated with an aqueous based thermoplastic, dried in an oven and used to reinforce asphalt roads. Alternatively, continuous glass fibers may be treated with a thermosetting resin and then pulled through a heated die to make parts such as ladder rails. This treatment of glass fibers is commonly referred to as "off-line" processing. In all cases, however, the continuous glass fibers must be spread apart, impregnated with resin and then recombined. This requirement almost always results in the use of additional hardware such as spreader bars, impregnation baths, and drying or curing ovens. These types of processes have the disadvantage that they add cost and complexity. In addition, in many cases, the resultant extra handling of the glass fibers can cause breakage of the individual glass filaments which can lead to reduced composite properties. Thus, while the off-line treatment methods may be effective, they are time consuming and inefficient and always require additional process steps beyond the glass forming step.
Gaa et al, U.S. Pat. No. 5,258,227, describes an aqueous chemical treatment which may be applied to glass fibers during the forming process and then dried. However, this method still requires that the fibers be wound into packages which are then dried at length in an oven.
Accordingly, there is still a need in the art for a method and apparatus for pre-impregnating glass fibers with a curable chemical treatment during the forming process which does not require additional drying steps, and which results in treated fibers having good handling and processing characteristics.